Hydraulic and lubricating fluid contamination sensor system

ABSTRACT

A method and apparatus for maintaining the rate of flow of hydraulic or lubricating fluid through a particle contamination sensor or monitor at an acceptable level is disclosed. The rate of flow may be a specific value or lie within a desired range of values. Regardless, maintaining the rate of flow at an acceptable level improves the accuracy of information produced by the contamination sensor or monitor. A display for displaying the particle information created by a particle contamination sensor or monitor in a manner more easily understood by maintenance personnel and a method of creating such a display is also disclosed.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/188,993, filed on Jul. 6, 2015, and U.S. Provisional Application No.62/104,555, filed on Jan. 16, 2015, the disclosures of both of which areincorporated herein by reference in their entirety.

BACKGROUND

As is well known to those familiar with hydraulic and lubricatingfluids, solid particle contaminants (hereinafter also “particlecontaminants” or just “contaminants”) in such fluids have a detrimentaleffect on the systems and devices that use such fluids, such ashydraulic control systems, hydraulic machines and motors, internalcombustion engines, etc. Solid particle contamination of hydraulic andlubricating fluids degrades such fluids, leading to the failure of thesystems and devices that use the fluids. Solid particle contaminatedhydraulic and lubrication fluids can cause internal leakage, which canlower the efficiency of the systems or devices employing such fluids.Further, solid particle contaminated hydraulic and lubricating fluid canimpact the ability of valves to control fluid flow and fluid pressure.Parts can stick to one another and seize when large amounts ofcontaminants accumulate. As a result, it is desirable and oftennecessary to regularly test hydraulic and lubricating fluid for particlecontaminants.

Testing can be done by withdrawing a small amount of fluid, transferringthe fluid to a testing laboratory, and testing the fluid forcontaminants. While usable, this procedure is both time consuming andexpensive and, therefore, generally unacceptable. This procedure is alsounacceptable due to the time delay between fluid withdrawal and fluidtesting. During this period of time, the system or device from which thefluid is withdrawn can be harmed if the fluid is contaminated.

As a result, machine installable contamination sensors have beendeveloped. Testing is accomplished by installing one or morecontamination sensors or monitors on a system or device employinghydraulic or lubricating fluid. An example of a contamination sensor isthe Hydac International CS 1000 Series Contamination Sensor. An exampleof a contamination monitor is the Schroeder Testmate® ContaminationMonitor. The CS 1000 Series Contamination Sensor and the SchroederTestmate® Contamination Monitor as well as other types of particlecontamination sensors and monitors measure solid particle contamination,usually optically, in hydraulic and lubricating fluid and outputinformation regarding the amount of particles in the fluid. The particleinformation may be presented in various sizes, such as >4, >6 and >14microns. The measurement results are provided according to variousstandards, such as International Standards Organization (ISO) Code 4406and SAE Aerospace standard AS4059, for example.

One of the major disadvantages of current hydraulic and lubricatingfluid contamination sensor systems is the need to maintain the flow ofthe fluid being monitored through the sensor either constant or at leastwithin an acceptable range. If the flow is not maintained constant orwithin an acceptable range, the particle information provided by thesensor becomes inaccurate. This can result in the inability to promptlyalert users to the occurrence of unacceptable particle contamination ofthe monitored hydraulic or lubricating fluid.

Another major disadvantage is the difficulty of easily interpreting theresults quickly and accurately either locally or remotely by maintenancepersonnel that are often unfamiliar with the nuances of the chosenoutput.

SUMMARY

Disclosed is a method and apparatus for maintaining the rate of flow ofhydraulic or lubricating fluid through a particle contamination sensoror monitor at an acceptable level. The rate of flow may be a specificvalue or lie within a desired range of values. Regardless, maintainingthe rate of flow at an acceptable level improves the accuracy ofinformation produced by the contamination sensor or monitor.

Also disclosed is a display for displaying the particle informationcreated by a particle contamination sensor or monitor in a manner moreeasily understood by maintenance personnel and a method of creating sucha display.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thedisclosed subject matter will become more readily appreciated as thesame become better understood by reference to the following detaileddescription, when taken in conjunction with the accompanying drawings,wherein:

FIG. 1 is a pictorial diagram of an exemplary hydraulic and lubricatingfluid contamination sensor system;

FIG. 2 is a pictorial diagram of another exemplary hydraulic andlubricating fluid contamination sensor system;

FIG. 3 is a functional flow diagram of an exemplary way of creating aflow control feedback signal suitable for use in the hydraulic andlubricating fluid contamination sensor systems shown in FIGS. 2 and 5;

FIG. 4 is a pictorial diagram of an exemplary display suitable for usein the hydraulic and lubricating fluid contamination sensor systemsshown in FIGS. 2 and 5;

FIG. 5 is a pictorial diagram of an exemplary remote hydraulic andlubricating fluid contamination sensor system; and

FIG. 6 is a block diagram of an exemplary remote oil contaminationsensor system for use with multiple sensors located on the same ordifferent apparatus.

EXEMPLARY EMBODIMENTS

FIG. 1 is a pictorial diagram of an exemplary hydraulic and lubricatingfluid contamination sensor system. More specifically, FIG. 1 includes avariable speed pump 11 and a contamination monitor 13 connected inseriatim to a hydraulic and lubricating fluid reservoir 15 via adelivery line or conduit 16. The hydraulic and lubricating fluidreservoir 15 represents a generic source of a hydraulic and lubricatingfluid whose solid particle contaminant content is to be monitored. Byway of example only, the reservoir 15 could be the oil reservoir of ahydraulic system, or the crank case of an internal combustion engine,either gasoline or diesel. Regardless of the nature of the hydraulic andlubricating fluid reservoir 15, the reservoir is connected to the inputof the variable speed pump 11 via the delivery line 16. The output ofthe variable speed pump 11 is connected to the input of thecontamination monitor via a suitable conduit 18. The output of thecontamination monitor is connected to the hydraulic or lubricating fluidreservoir 15 via a return line or conduit 20.

Since it is not important to the disclosed hydraulic and lubricatingfluid contamination sensor system, the hydraulic or other system,gasoline or diesel engine or other system, apparatus, or device thatincorporates the reservoir 15 is not disclosed. Further, as will bebetter understood from the following discussion, rather than a fluidreservoir, the variable speed pump 11 could receive fluid whose particlecontamination content is to be monitored from some other source, such asa line of a hydraulic system. The fluid delivery and return lines orconduits 16 and 20 and, thus, the variable spaced pump 11 andcontamination monitor 13 could parallel an operational line of ahydraulic or other system, apparatus, or device.

One example of a suitable variable speed pump is the FG SeriesPump-Motor Unit available from Fluid-O-Tech International Inc.,Plantsville, Conn. This exemplary pump-motor unit includes an analogvoltage control input. The magnitude of the analog voltage controls thespeed of the motor and, thus, the fluid flow rate through the motor pumpunit. See Appendix A of Provisional Application No. 62/104,555, thesubject matter of which is incorporated herein by reference, for moredetail regarding this exemplary variable speed motor pump unit.

One example of a suitable contamination monitor is the HydacInternational CS 1000 Series Contamination Sensor available from HydacFiltertechnik GmbH, Saar, Germany. See Appendix B of ProvisionalApplication No. 62/104,555, the subject matter of which is incorporatedherein by reference, for more detail regarding this exemplarycontamination monitor. The CS 1000 Series Contamination Sensor, which isillustrated in FIG. 1, includes a display 17 that, depending on thedisplay state of the monitor, can display any one of a plurality ofparameters including, but not limited to, ISO particle count, SAEparticle count, and flow rate.

Also illustrated in FIG. 1 is a manual flow control 21 and a user 23.The manual flow control 21 is connected to the variable speed pump 11.In the case of the exemplary FG Series Pump-Motor Unit, the manual flowcontrol 21 can be a simple rheostat operated by the user 23 to controlthe voltage applied to the control input of this exemplary variablespeed pump 11. Obviously, other types of variable speed pumps mayrequire a different type of manual flow control.

In operation, the contamination monitor is placed in its flow displaystate. As necessary, the user 23 operates the manual flow control 21 tochange the speed of the variable speed pump 11 until the displayed flowis at a predetermined value or falls within a predetermined range, asappropriate. The contamination monitor is then changed to the ISO or SAEparticle display state to display the particle contamination state ofthe hydraulic or lubricating fluid pumped through the contaminationmonitor 13 by the variable speed pump 11. Because the flow is maintainedat a predetermined value or within a predetermined range, the accuracyof the ISO or SAE particle display is maintained valid.

Like the embodiment illustrated in FIG. 1, the embodiment illustrated inFIG. 2 includes a variable speed pump 25 and a contamination monitor 27.The variable speed pump is connected to a hydraulic or lubricating fluidreservoir 29 via a delivery line or conduit 30 and pumps fluid to thecontamination monitor 27. While the variable speed pump 25 is similar tothe variable speed pump 11 illustrated in FIG. 1, the contaminationmonitor 27 illustrated in FIG. 2 is shown mounted on a support block 35.Such an arrangement is shown in Appendix B of Provisional ApplicationNo. 62/104,555, which has been incorporated herein by reference. Thehydraulic or lubricating fluid pumped by the variable speed pump 25 issupplied to the support block 35 via an input line or conduit 36. Thesupport block 35 supplies the fluid to the contamination monitor 27.Fluid is returned to the reservoir 29 via a return line or conduit 38.Also mounted on the support block 35 is an aqua sensor 33. An exemplaryaqua sensor is the AS1000 AquaSensor available from Hydac International,which is described in Appendix C of Provisional Application No.62/104,555, the subject matter of which is also incorporated herein byreference. Like the contamination monitor 27, the aqua sensor 33receives fluid from the support block 35.

The contamination monitor 27 includes a display 31 and may be the sameas the contamination monitor 13 shown in FIG. 1. An electrical output ofthe contamination monitor 27 that is connected to an interface module 37provides information to the interface module 37 that is similar to aninformation displayed by the display 31. An electrical output of theaqua sensor 33 is also connected to the interface module 37.

While various information signals are produced by the contaminationmonitor 31 and the aqua sensor 33, only the ones of importance to thisdisclosure are discussed here. These are the signals that contain flowand particle count information produced by the contamination monitor andtemperature and water content information produced by the aqua sensor.As noted above, these signals are sent to the interface module 37. Theinterface module is connected to a computer or other signalinterpretation device 39. The computer can be a desktop computer(illustrated) or a laptop computer or some specialized programmable orprogrammed computing device that includes a display.

In addition to receiving information signals, the interface modulegenerates a flow control feedback signal that is applied to the controlinput of the variable speed pump 25. Either based on the program of amicroprocessor included in the interface module 37 or in response toinstructions received from a program installed on the computer 39, theinterface module analyzes the flow information received from thecontamination monitor 27 and controls the flow control feedback signalsuch that the flow passing through the contamination monitor ismaintained at an acceptable constant value or within an acceptablepredetermined range.

FIG. 3 is a functional flow diagram of an exemplary way of creating aflow control feedback signal suitable for use in FIG. 2 provided byeither the interface module 37 or the computer 39 depending upon how theFIG. 2 embodiment is implemented. In general, the flow portion of theflow and particle data received from contamination monitor 27 isanalyzed in a series of tests. In accordance with results of the tests,the speed of the variable speed pump 25 is controlled. Controlling thespeed of the variable speed pump controls the rate of fluid flow throughthe contamination monitor 31. Five sequential tests are included in FIG.3, the order of which can be changed if desired. The first test 41determines if there is any fluid flow. If there is no fluid flow, powerto the variable speed pump is turned off 43. No fluid flow indicates aproblem with the system, such as a lack of fluid. As a result, thevariable speed pump is shut down. If fluid is flowing, next, a test 45is made to determine if the rate of flow is very fast. If so, the pump'sspeed is changed (reduced) so as to reduce the flow 47 to an acceptablelevel. If the flow rate is not very fast, next, a test 49 is made todetermine if the flow rate is fast, but not very fast. If the flow rateis fast, the pump's speed is again changed (reduced) so as to reduce theflow 51 to an acceptable level. Next, if the flow rate is not fast, atest 53 is made to determine if the flow rate is slow. If the flow rateis slow, the pump's speed is changed (increased) to increase the rate offlow 55 to an acceptable level. If the flow rate is not slow, next atest 57 is made to determine if the flow rate is very slow. If the flowrate is really slow, the pump's speed is changed (increased) to increasethe rate of flow 59 to an acceptable level. If the flow rate is not veryslow, the flow rate is deemed to be at an acceptable level and no actionis taken 61.

As will be understood from the foregoing description, the embodimentillustrated in FIG. 2 includes an automatic feedback control system thateliminates the need for a user to manually control the flow of fluidpassing through the contamination monitor 35 in order to maintain theflow at an acceptable constant value or within an acceptable range.

Returning to FIG. 2, the display of the computer 39 displays theinformation produced by the contamination monitor 31 and the aqua sensor33 including, but not limited to, flow and particle count informationand temperature and water content information. An exemplary computerdisplay 62 suitably for use in FIG. 2 is illustrated in FIG. 4. If thedisplay is to be transmitted to a remote location, it may be in the formof a web page.

The display illustrated in FIG. 4 includes a plurality of regions. Onthe left side is a vertical array of three rotary widget dials 63, 64,and 65. The operation of the rotary widget dials are controlled bysoftware widgets. Software widgets are small computer applications thathave limited functionality. Widget displays, as shown in FIG. 4,normally occupy a small area of web page (display) and displayinformation fetched from other locations, e.g., web sites. Widgets areusually created in DHTML or Adobe Flash.

Across the top, above a graph 67, is a horizontal list of timeincrements 69. In this exemplary display, the illustrated timeincrements are two hours, one day, one week, one month, and one year. Asnoted by the circles located to the left of each of these intervals, theintervals are selectable with the two-hour interval being selected inFIG. 4 as shown by the dark dot inside the circle. Only one interval isselectable at a time. The chosen interval controls the time interval ofthe graph 67. The time interval is located on the horizontal axis of thegraph 67. Selection is done in accordance with conventional computercontrol technology using a mouse, stylus, etc.

To the right of the time increment list 69 is an auto-refresh selectionarea 71, which allows the graph to be automatically refreshed if anauto-refresh element is selected. Again, selection is accomplished inany conventional, well-known computer control technology manner.

The graph 67 is a three-element running graph that shows particle countsover the chosen time interval, two hours in the illustrated example. Onegraph element is designated ISO 4, the second graph element isdesignated ISO 6, and the third graph element is designated ISO 14. Thenumbers 4, 6, and 14 relate to particle count in microns based on ISOstandards. ISO particle count value is shown on the vertical axis of thegraph 67, on the left side thereof.

The graph element identifiers are also associated with the three widgetdials 63, 64, and 65 located on the left side of FIG. 4 with ISO 4associated with the upper dial 63, ISO 6 associated with the middle dial64, and ISO 14 associated with the lower dial 65, as shown by therelated ISO 4, ISO 6, and ISO 14 identifiers on the widget dials.

Located beneath the graph 67 is a table area 73 that includes aplurality of columns. The first (leftmost) column is designated a COUNTcolumn, the second column moving to the right is designated a DATEcolumn, the third column is designated a TIME column, the fourth columnis designated ISO 4, the fifth column is designated ISO 6, and the sixthcolumn is designated ISO 14. The seventh or last column is designatedtemperature in degrees Fahrenheit (TEMP F°). The COUNT column is avertical seriatim list of numbers used to identify the information inthe other columns. The DATE column sets forth the date when a particularcount was recorded, the TIME column designates the time when aparticular count was recorded. The ISO 4, ISO 6, and ISO 14 columnscontain the particle values measured when the particular count wasrecorded. The TEMP F.° column provides information about the temperatureof the hydraulic or lubrication fluid when a particular count wasrecorded.

Located to the right of the table 73 is a sensor limits box 75. Thesensor limits box sets forth the maximum and minimum values for the ISO4, ISO 6, and ISO 14 data that produce the count values shown in thetable 33.

In operation, obviously, the table 67 provides a running ISO particlecount value of the sensed ISO 4, ISO 6, and ISO 14 data. The widgetsreceive the same information or data and the rotary widget dials 63, 64,and 65 display the data in an instantaneous manner. As illustrated bystippling, the widget dials include various color-coded areas located inan arc. In one exemplary embodiment, a very low particle area (a) isgray, followed by a green area (b), followed by a yellow area (c),followed by a red area (d). Each area relates to a range of particlecount values starting with zero at the beginning end of the gray (a)area and ending at 65 at the ending end of the red (d) area. A needle(e) that moves across a dial, in a conventional manner, points to theactual particle count. In addition to the value being shown by theneedle/dial combinations, a numerical value is shown in a box 81included at the bottom of each of the rotary widget dials 63, 64, and65.

As will be readily appreciated from the foregoing description, when thewidget dial arrows are in the gray (a) or green (b) areas, the ISOparticle count is acceptable. When in the yellow (c) area, the ISO countis still acceptable, but less than desirable. When in the red (d) area,the ISO particle count is unacceptable.

In addition to providing the display shown in FIG. 4, text or e-mailmessages can be provided to a user access device or some other suitablealert device when an ISO count reaches the red area of one of the widgetdials.

As will be readily appreciated by those skilled in the art, the displayillustrated in FIG. 4 should be considered as exemplary and not aslimiting. The layout of the various components of the display can bearranged differently. Some components may be deleted and others addeddepending on the needs of the end user.

The embodiment illustrated in FIG. 5 includes all of the elements of theembodiment illustrated in FIG. 2, plus remote display and controldevices. More specifically, the computer 39 is illustrated as connectedvia a network, such as the Internet 85, to remote display and controldevices such as a client desktop computer 87 or a client mobile device89, which can take the form of a smart phone, a personal digitalassistant, a laptop computer, etc. The information received by thecomputer 39 illustrated in FIG. 1 is transmitted to the remote devicesvia the Internet 85. This allows remotely located users to monitor theoperation of the contamination monitor 27 and control the flow controlfeedback signal, if needed, by changing the acceptable constant value orthe acceptable range, as also can be done by the computer 39.

FIG. 6 is a block diagram of an exemplary remote oil contaminationsensor system 91 suitable for monitoring a plurality of devices that usehydraulic or lubricating fluid, or a plurality of regions of a singledevice. The results are remotely displayable on a single or a pluralityof monitoring devices. More specifically, the illustrated remote oilcontamination sensor system 91 comprises: a plurality of data collectors93; a plurality of fluid particle sensors 95; a cloud service 97; and aplurality of access devices 99, each of which includes a display 101.The plurality of data collectors 93 and particle sensors 95, which areshown in block form in FIG. 6, may be formed by elements connected tothe computer 39 shown in FIGS. 2 and 5, for example.

One or more of the particle contamination sensors 95 are connected toeach of the data collectors 93. More specifically, depending onimplementation, a single particle contamination sensor 95 may beconnected to a single data collector 93. Such an implementation might beused when a particle contamination sensor is associated with a singlehydraulic system or a single device that employs hydraulic orlubricating fluid. Alternatively, in other implementations, a pluralityof particle contamination sensors 95, each associated with a singlehydraulic system or device, may be connected to a single data collector95. Such an embodiment might be used with a large hydraulic system ordevice so that hydraulic or lubricating fluid contamination can bedetected at various locations. Still further, each of the particlecontamination sensors 95 can be associated with a separate hydraulicsystem or device. As a result, FIG. 6 should be taken as exemplary andnot limiting.

Data produced by the particle contamination sensors 95 is collected bythe related data collector 93. While, preferably, data is collected atregular intervals, if desired, the collection intervals can vary intime. For example, the collection intervals can be different when theassociated hydraulic system or device is running, as opposed to whenidled or shut down. While the particle contamination sensors 95 areillustrated as “hard wired” to their related data collectors 93,obviously the sensors can be wirelessly connected, if desired. While thedata collectors 93 can take on various forms, in one actual embodimentof the disclosed subject matter, the data collectors are formed by localprocessors, specifically, a small computer running a Linux operatingsystem. For example, the computer 39 shown in FIG. 5.

The cloud service 97 is a conventional cloud service comprised of aplurality of servers formed by one or more server farms. As is wellknown to those skilled in the art, a cloud service can provide virtualprivate servers to users of the cloud service, one of which 98 isassociated with the disclosed subject matter and shown in FIG. 6. In oneactual embodiment of the disclosed subject matter, the virtual privateserver 98 included in the cloud service and associated with thedisclosed subject matter is a virtual private server running a Linuxoperating system.

While a hard wire connection could be made between the data collectorsand the cloud service, preferably, as illustrated, the connection is awireless connection. More specifically, the connection between the datacollectors 93 and the cloud service can be a WiFi connection, a wiredInternet connection, a cell phone signal connection (GSM, CDMA, andLTE), or any other wired or wireless data connection known in the art.

The access devices 99 can take any one of a plurality of forms, personalcomputer (desktop or laptop), personal digital assistant (PDA), cellphone, etc. Regardless of the nature of a specific access device, eachof the illustrated access devices includes or is connected to a display101.

In operation, each of the data collectors 93 collect data from the oneor more particle contamination sensor 95 connected to the datacollector. The collected data is formatted in a conventional dataformat, such as the ISO 4406:99 data format. That is, as shown in FIG. 4and previously described, the data may be tabulated in the ISO form ofA, B, and C, where A represents the number of particles greater than 4microns, B represents the number of particles greater than 6 microns,and C represents the number of particles greater than 14 microns. Inessence, the data collectors convert current sensor data into a formsuitable for creating a more user friendly display, such as the displayillustrated in FIG. 4 and described above. The data collectors 93transmit the collected, converted data to the virtual private server 98included in the cloud service 97. The virtual private server stores thereceived data, thereby making this collected data available forretrieval by the access devices 99. The access devices 99 retrieve thedata stored on the virtual private server and use the retrieved data tocreate a user friendly display, an example of which is illustrated inFIG. 4 and described above.

As will be readily appreciated from the foregoing description, both thelocal and remote hydraulic/lubricating contamination sensor systems andmethods described above, in addition to providing contaminationinformation in real time, provide the information in a form that isreadily usable by maintenance and other personnel unfamiliar with thenuances of ISO and other standard codes. In essence, the oilcontamination sensor system includes local processors that collect datafrom one or more particle counters mounted in machines being monitored.The particle count data is in ISO 4406 or some other standard code. Inthe illustrated FIG. 2-6 embodiments, the particle data falls in threecategories designated ISO 4, ISO 6, and ISO 14, where the 4, 6, and 14refer to the size of the particles in microns being counted. The localprocessor stores the received data and transmits it to a larger storagedevice, such as a virtual private server included in a cloud service,presumably at regular intervals. The data is presented to the end useras a display, in preferably a remotely transmittable Web page displaythat contains widgets. While shown as rotary display widgets, obviously,the widget displays can take on other forms—linear, for example. Ifdesired, the display or Web page can include other information, such asthe collected ISO code data and graphs. The end result is an oilcontamination sensor system that provides data in a relatively simpleand easily understood form to a remote location, i.e., a location remotefrom the system or device whose hydraulic or lubrication fluid is beingmonitored. In this regard, “remote” should be construed broadly andinclude, for example, a location in the same building as the system ordevice including a location near the system or device. In suchenvironments, the cloud service shown in FIG. 6 may not be required.Rather, data from the data collectors may be presented directly to theaccess device wirelessly or via wires, encrypted or unencrypted asdesired. In addition to presenting contamination data in a relativelyeasy-to-understand form, if desired, text and/or e-mail messages can besent to an end user when particle contaminants are at or approaching acritical stage. Further, information in addition to that shown in FIG. 4can be displayed either or both as widget (instantaneous) data orrunning data, such as temperature, moisture content, or saturationlevel, for example. Max/min values can also be displayed for such otherdata. While preferred embodiments have been illustrated and described,it will be appreciated that various changes can be made therein withoutdeparting from the spirit and scope of the disclosed subject matter.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A fluid contaminationmonitor system comprising: a variable speed pump that receives fluidwhose particle contamination is to be monitored and supplies the fluidto a contamination monitor at a controllable rate of flow; acontamination monitor that receives the fluid whose particlecontamination is to be monitored from said variable speed pump, saidcontamination monitor generating information regarding the rate of flowof the fluid received from the variable speed pump and displayinginformation regarding the particle contamination of the fluid; and acontroller that controls the operation of the variable speed pump so asto keep the rate of flow at a target level.
 2. The fluid contaminationsensor system as claimed in claim 1, wherein the target level lieswithin a range of values.
 3. The fluid contamination monitor system asclaimed in claim 1, wherein said target level is a predetermined value.4. The fluid contamination monitor system as claimed in claim 1, whereinsaid controller manually controls the operation of the variable speedpump in accordance with user input.
 5. The fluid contamination monitorsystem as claimed in claim 1, wherein the contamination monitor producesinformation indicating the rate of flow of the fluid received from saidvariable speed pump and the controller receives the rate of flowinformation and includes a program that controls the operation of thevariable speed pump so as to keep the rate of flow at said target level.6. The fluid contamination monitor system as claimed in claim 1,including a display that displays information regarding the particlecontamination of the fluid.
 7. The fluid contamination monitor system asclaimed in claim 6, wherein the display includes a plurality of elementseach displaying the level of contamination of particles having a sizegreater than a predetermined value.
 8. The fluid contamination monitorsystem as claimed in claim 1, wherein the fluid comprises at least oneof a hydraulic fluid and a lubricating fluid.
 9. A method of determiningthe particle contamination of a fluid, comprising the steps of:controlling the rate of flow of the fluid whose particle contaminationis to be monitored such that the rate of flow is at a target level; andmonitoring the flow of fluid whose rate is controlled and producinginformation regarding the particle contamination of the fluid.
 10. Themethod of determining the particle contamination of a fluid as claimedin claim 9, wherein the target level lies within a range of values. 11.The method of determining the particle contamination of a fluid asclaimed in claim 9, wherein the target level is a predetermined value.12. The method of determining the particle contamination of a fluid asclaimed in claim 9, wherein the rate of flow of the fluid whose particlecount is to be monitored is manually controlled by a user.
 13. Themethod of determining the particle contamination of a fluid as claimedin claim 9 further comprising the steps of producing informationregarding the rate of flow of the fluid whose particle contamination isto be monitored and automatically controlling the rate of flow based onsaid information.
 14. The method of determining the particlecontamination of a fluid as claimed in claim 9, further comprising thestep of displaying information regarding the particle contamination ofthe fluid whose particle contamination is to be monitored.
 15. Themethod of determining the particle contamination of a fluid as claimedin claim 14, wherein the displaying step comprises the step ofdisplaying a plurality of regions, each region displaying the level ofcontamination of particles having a size greater than a predeterminedvalue.
 16. The method of determining the particle contamination of afluid as claimed in claim 9, wherein the fluid comprises at least one ofa hydraulic fluid and a lubricating fluid.